Object detection device

ABSTRACT

An object detection apparatus is mounted to a vehicle and detects an object by a reflected wave of a probe wave. The object detection apparatus calculates a relative velocity of the object to the vehicle, estimates an azimuth of the object relative to the vehicle, and corrects the estimated azimuth. The object detection apparatus generates a velocity-azimuth curve that indicates a relationship between the relative velocity of the object and the azimuth of the object that is calculated based on a theoretical mounting angle of the object detection apparatus, supplies a weight to an azimuth error that is an error between the velocity-azimuth curve and the estimated azimuth, based on the estimated azimuth, and calculates a correction value of the estimated azimuth by calculating, as an actual mounting angle deviation of the object detection apparatus, a weighted average value of the azimuth error to which the weight is supplied.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalApplication No. PCT/JP2020/040006, filed on Oct. 23, 2020, which claimspriority to Japanese Patent Application No. 2019-198744, filed on Oct.31, 2019. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND Technical Field

The present disclosure relates to an object detection apparatus.

Related Art

An object detection apparatus such as an onboard radar apparatus isknown. The object detection apparatus may be mounted to a vehicle anddetect an object by a reflected wave of a probe wave.

SUMMARY

One aspect of the present disclosure provides an object detectionapparatus that is mounted to a vehicle and detects an object by areflected wave of a probe wave. The object detection apparatuscalculates a relative velocity of the object to the vehicle, estimatesan azimuth of the object relative to the vehicle, and corrects theestimated azimuth. The object detection apparatus generates avelocity-azimuth curve that indicates a relationship between therelative velocity of the object and the azimuth of the object that iscalculated based on a theoretical mounting angle of the object detectionapparatus, supplies a weight to an azimuth error that is an errorbetween the velocity-azimuth curve and the estimated azimuth, based onthe estimated azimuth, and calculates a correction value of theestimated azimuth by calculating, as an actual mounting angle deviationof the object detection apparatus, a weighted average value of theazimuth error to which the weight is supplied.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram illustrating a configuration of an objectdetection apparatus;

FIG. 2 is a diagram for explaining a position in which the objectdetection apparatus is set, and a relative position and an azimuth of anobject;

FIG. 3 is a diagram illustrating a relationship between an observationpoint and a velocity-azimuth curve;

FIG. 4 is a flowchart illustrating an object detection process;

FIG. 5 is a flowchart illustrating an azimuth correction valuecalculation process; and

FIG. 6 is a diagram for explaining weighting based on azimuth.

DESCRIPTION OF THE EMBODIMENTS

The following embodiments of the present disclosure relate to an objectdetection apparatus that is mounted to a vehicle and detects an objectby a reflected wave of a probe wave.

As described in Japanese Patent Publication No. 6358076, in a case inwhich an object detection apparatus, such as an onboard radar apparatus,that detects an object by a reflected wave of a probe wave is mounted toa bumper of a vehicle, detection performance regarding an azimuth atwhich the object is present is known to decrease as a result ofdeviation of a mounting angle of the object detection apparatus(deviation from a theoretical mounting angle of the object detectionapparatus). To improve detection accuracy regarding the azimuth of theobject, an azimuth error that is a detection error of the azimuth of theobject that is attributed to the deviation of the mounting angle ispreferably calculated.

In Japanese Patent Publication No. 6358076, the azimuth error iscalculated by a comparison of a velocity-azimuth curve and anobservation point, the velocity-azimuth curve being calculated based onthe theoretical mounting angle of the object detection apparatusregarding a relationship between a relative velocity of the objectrelative to an own vehicle and the azimuth of the object. Then, anactual mounting angle is calculated from the azimuth error and thedetected azimuth of the object is corrected.

When a vehicle velocity error that is an error in a velocity of the ownvehicle is present, the velocity-azimuth curve in Japanese PatentPublication No. 6358076 becomes a velocity-azimuth curve that includesthe vehicle velocity error and deviation occurs. Consequently,calculation accuracy regarding the azimuth error and the mounting anglemay decrease, and further, calculation accuracy regarding the detectedazimuth of the object may decrease.

It is thus desired to provide a technology that enables an azimuth of anobject to be accuracy detected in an object detection apparatus, evenwhen a vehicle velocity error is present.

An exemplary embodiment of the present disclosure provides an objectdetection apparatus that is mounted to a vehicle and detects an objectby a reflected wave of a probe wave. The object detection apparatusincludes: a velocity calculating unit that calculates a relativevelocity of the object to the vehicle; an azimuth estimating unit thatestimates an azimuth of the object relative to the vehicle; and anazimuth correcting unit that corrects the azimuth of the object relativeto the vehicle that is estimated by the azimuth estimating unit.

The azimuth correcting unit includes: a velocity-azimuth curvegenerating unit that generates a velocity-azimuth curve that indicates arelationship between the relative velocity of the object and the azimuthof the object that is calculated based on a theoretical mounting angleof the object detection apparatus; a weighting unit that supplies aweight to an azimuth error that is an error between the velocity-azimuthcurve and the estimated azimuth, based on the azimuth that is estimatedby the azimuth estimating unit; and a correction value calculating unitthat calculates a correction value of the estimated azimuth bycalculating, as an actual mounting angle deviation of the objectdetection apparatus, a weighted average value of the azimuth error towhich the weight is supplied by the weighting unit.

As a result of keen research, the present disclosures have obtainedknowledge that a deviation amount that occurs in the velocity-azimuthcurve as a result of a vehicle velocity error changes based on theazimuth of the object relative to the vehicle. Based on this knowledge,the object detection apparatus related to the present disclosure firstestimates the azimuth of the object relative to the vehicle by theazimuth estimating unit. Then, the weighted average of the azimuth errorto which the weight is supplied based on the estimated azimuth iscalculated as the mounting angle deviation and the correction value ofthe azimuth is calculated by the azimuth correcting unit. Therefore, themounting angle deviation of the object detection apparatus can bemitigated taking into consideration the deviation amount that occurs inthe velocity-azimuth curve as a result of the vehicle velocity error.Consequently, the azimuth of the object can be accurately detected evenwhen the vehicle velocity error is present.

An object detection apparatus 10 shown in FIG. 1 is an apparatus fordetecting an object by a reflected wave of a probe wave. As shown inFIG. 2, for example, the object detection apparatus 10 may be mounted toan own vehicle 40 by being mounted to a rear bumper 41 or the like ofthe own vehicle 40. The rear bumper 41 is composed of a material thattransmits electromagnetic waves, such as radar waves. The objectdetection apparatus 10 is set near a right end within the rear bumper41.

The object detection apparatus 10 includes an antenna unit 11, atransmitting/receiving unit 12, and a signal processing unit 20. Theobject detection apparatus 10 is communicably connected to otherapparatuses that are mounted to the vehicle by an onboard local areanetwork (LAN) (not shown).

The antenna unit 11 includes a plurality of antennas that are arrayed ina single row in a horizontal direction. The antenna unit 11 transmitsand receives radar waves that are composed of multifrequency continuouswaves (CW).

The transmitting/receiving unit 12 periodically transmits and receivesthe radar waves as probe waves at a fixed time interval, through theantenna unit 11. In addition, for every reception signal that isreceived by the antennas that configure the antenna unit 11, thetransmitting/receiving unit 12 generates a beat signal that is composedof a frequency component that is a difference between the receptionsignal and a transmission signal, and supplies reception data that isthe beat signal to which analog-to-digital (A/D) conversion is performedto the signal processing unit 20. Here, the multifrequency CW iscomposed of a plurality of continuous waves that are of the order of GHzand of which frequencies differ by about 1 MHz.

The signal processing unit 20 is a known microcomputer that is mainlyconfigured by a central processing unit (CPU), a read-only memory (ROM),and a random access memory (RAM). The signal processing unit 20 detectsan object that reflects the radar wave and performs at least a mainprocess for generating information related to the object based on aprogram that is stored in the ROM. Here, a portion of the RAM isconfigured by a non-volatile memory in which contents of the memory areheld even when power of the object detection apparatus 10 is turned off.The non-volatile memory stores therein an azimuth correction table thatindicates a corresponding relationship between a relative velocity to anobject (here, a frequency bin that is obtained by frequency analysis)and an azimuth error at this relative velocity.

The signal processing unit 20 includes an object detecting unit 21, avelocity calculating unit 22, an azimuth estimating unit 23, and anazimuth correcting unit 30.

For example, the object detecting unit 21 can acquire a reflected waveof a radar wave that is received by the transmitting/receiving unit 12and detect an object by analyzing the reflected wave.

When the object is detected, the velocity calculating unit 22 calculatesa relative velocity of the detected object relative to the own vehicle40. For example, the relative velocity can be calculated from thereflected wave of the radar wave that is received by thetransmitting/receiving unit 12. More specifically, the relative velocityof the object to the own vehicle 40 can be calculated by a frequency ofthe reflected wave of the radar wave that is reflected by the objectthat changes as a result of the Doppler effect.

When the object is detected, the azimuth estimating unit 23 estimates anazimuth of the detected object relative to the own vehicle 40. Forexample, the azimuth of the object can be calculated by a phasedifference of the reflected wave of the radar wave that is received bythe plurality of antennas in the transmitting/receiving unit 12. Here, adistance between the own vehicle 40 and the object can be calculated bya transmission time of the radar wave and a reception time of thereflected wave. In addition, if the position and the azimuth of theobject are calculated, a relative position of the object to the ownvehicle 40 can be identified.

The azimuth correcting unit 30 corrects the azimuth (referred to,hereafter, as an estimated azimuth) of the object to the own vehicle 40that is estimated by the azimuth estimating unit 23. The azimuthcorrecting unit 30 includes an observation-point distribution generatingunit 31, a velocity-azimuth curve generating unit 32, a weighting unit33, and a correction value calculating unit 34.

When the object detecting unit 21 detects an object, theobservation-point distribution generating unit 31 generates objectinformation for the detected object that includes at least the relativevelocity that is calculated by the velocity calculating unit 22 and theazimuth that is estimated by the azimuth estimating unit 23, andgenerates an observation point distribution P shown in FIG. 3. Theobservation point distribution P includes an N number of observationpoints for the object. A relative velocity Vok and an estimated azimuthθok of the object are associated with a kth observation point (k=1, . .. , N).

The velocity-azimuth curve generating unit 32 acquires a relativevelocity Vo of the object that is calculated by the velocity calculatingunit 22 and a vehicle velocity Vc and generates a velocity-azimuth curveC. For example, as the vehicle velocity Vc, a detection value of avehicle velocity sensor can be acquired. When a stationary object suchas a wall surface is present on a righthand side of the own vehicle 40,the reflected wave can be acquired from various points on the wallsurface. In addition, an azimuth at which the observation point on thewall surface is present and a relative velocity that is detected for theobservation point have a relationship that is expressed by thevelocity-azimuth curve C.

As shown in FIG. 2, a case in which the object detection apparatus 10 ismounted to a vehicle in a direction indicated by a broken line 51 thatis tilted by a mounting angle θr [deg] to the right when viewed fromabove the own vehicle 40, relative to a front/rear direction of thevehicle 40 indicated by a broken line 50 is described as an example.When the object that reflects the radar wave is a stationary object, acorresponding relationship that is expressed in expression (2) belowthat is also shown in FIG. 2 is present between the relative velocity ofa stationary object to the side and the azimuth at which the stationaryobject is present. In addition, a mounting angle deviation Od of theobject detection apparatus 10 can be calculated by expression (1) belowthat is also described in FIG. 2.

$\begin{matrix}{{\theta\; d} = {{{\theta\; r} - {\theta\; b}} = \frac{\sum_{k = 0}^{N}\left( {{\theta\;{ik}} - {\theta\;{ok}}} \right)}{N}}} & (1) \\{{\theta\;{ik}} = {{a{\cos\left( \frac{Vok}{{- {Vci}} \times {Ve}} \right)}} + {\theta\; b}}} & (2)\end{matrix}$

Here, θr is an actual mounting angle of the object detection apparatus10. θb is a theoretical mounting angle (a mounting angle when adeviation in angle is not present). θik is an azimuth at the kthobservation point of the object that is calculated based on θb. θok isan azimuth (that is, an estimated azimuth) that is observed at the kthobservation point of the object. Vci is a true vehicle velocity of theown vehicle 40. Vok is a relative velocity at the kth observation pointof the object. Ve is a velocity error (error in Vc). N is a total numberof observation points of the object. Units of θd, θr, θik, θok, and θbare all radian (rad). Here, the detected vehicle velocity Vc of the ownvehicle 40 can be expressed by Vc=Vci×Ve.

The velocity-azimuth curve generating unit 32 generates thevelocity-azimuth curve C based on expression (2) above that is alsoshown in FIG. 2. That is, the velocity-azimuth curve C is a curve thatindicates the relationship between the relative velocity Vo of theobject and the azimuth θi of the object that are calculated based on atheoretical mounting angle θb of the object detection apparatus 10.

When a range of laser probe in the object detection apparatus 10 is 0 to180 [deg], a probe range is a range that is behind the broken line 51relative to the own vehicle (a range on a lower side in FIG. 2). Abroken line 52 indicates an estimated azimuth θo that is an azimuth ofthe detected object. The estimated azimuth θo corresponds to an anglethat is formed by the broken line 51 and the broken line 52. When aprobe range that is below and to the left of the broken line 51 in FIG.2 is 0 [deg] and a probe range that is above and to the right is 180[deg], a directly lateral direction to the own vehicle 40 (a rightwarddirection to the own vehicle 40 that is orthogonal to the vehiclevelocity Vc) is 90+θr [deg].

As shown in FIG. 2, the relative velocity Vo of the detected object canbe expressed by Vo=−Vc×cos (θo−θr). When a point that is directlylateral to a position in which the object detection apparatus 10 ismounted is an observation point, because θo=90+θr [deg], the relativevelocity Vo at this observation point is 0. That is, the azimuth at anintersection between the velocity-azimuth curve C shown in FIG. 3 and anazimuth axis (θ axis) is 90+θr [deg]. The relative velocity Vo of anobservation point that is positioned further toward an advancingdirection side of the own vehicle 40 than the directly lateralobservation point is a positive value that indicates moving toward theown vehicle 40. In addition, the relative velocity Vo of an observationpoint that is positioned further toward a side opposite the advancingdirection of the own vehicle 40 than the directly lateral observationpoint is a negative value that indicates moving away from the ownvehicle 40.

That is, when θ>90+θr [deg], the relative velocity Vo is Vo>0. Whenθ<90+θr [deg], the relative velocity Vo is Vo<0. In addition, when adirection that is directly behind the own vehicle 40 is an observationpoint, because θ=θr, the velocity-azimuth curve C becomes a localminimum value and the relative velocity Vo=−Vc. That is, thevelocity-azimuth curve C has a linearly symmetrical shape at the azimuthθr that is the direction directly behind the own vehicle.

As shown in FIG. 3, the velocity-azimuth curve C changes based on avalue of a vehicle velocity error Ve. In FIG. 3, the velocity-azimuthcurve C that is shown by a solid line shows the velocity-azimuth curvewhen the vehicle velocity error Ve is 1 (Ve=1). The velocity-azimuthcurve C that is shown by a broken line shows the velocity-azimuth curvewhen the vehicle velocity error Ve is greater than 1 (Ve>1). In contrastto when Ve=1, when Ve>1, the velocity-azimuth curve C has a smaller rateof change of the relative velocity Vo relative to the azimuth θ. Inaddition, in both of when Ve>1 and when Ve<1, a deviation amount of thevelocity-azimuth curve C increases as the relative velocity Vo becomesfarther from zero.

As shown in FIG. 3, the azimuth error at each observation point isexpressed by a difference (θik−θok) in the azimuth-axis direction(left/right direction in FIG. 3) between the velocity-azimuth curve Cand each point that is included in the observation point distribution P.Through expression (1) above, the mounting angle deviation θd can becalculated by a total average of the azimuth error at each observationpoint being calculated. It can be understood that, when thevelocity-azimuth curve C is deviated as a result of the vehicle velocityerror Ve, the azimuth error is also deviated, and the mounting angledeviation θd that is calculated by expression (1) above is also deviatedas well.

In comparison to the velocity-azimuth curve when Ve=1, when Ve>1, thevelocity-azimuth curve is deviated toward a direction that is closer tothe observation point distribution P side as the relative velocitybecomes faster toward an approaching side, and the velocity-azimuthcurve is deviated toward a direction that is farther from theobservation point distribution P side as the relative velocity becomesfaster toward a separating side. Therefore, when Ve>1, the azimuth erroris calculated to be smaller as the relative velocity becomes fastertoward the approaching side, and the azimuth error is calculated to begreater as the relative velocity becomes faster toward the separatingside.

In contrast, when Ve<1, the velocity-azimuth curve is deviated toward adirection that is farther from the observation point distribution sidewhen the relative velocity becomes faster toward the approaching side,and the velocity-azimuth curve is deviated in a direction that is closerto the observation point distribution P side as the relative velocitybecomes faster toward the separating side. Therefore, when Ve<1, theazimuth error is calculated to be greater as the relative velocitybecomes faster toward the approaching side, and the azimuth error iscalculated to be smaller as the relative velocity becomes faster towardthe separating side. In both of when Ve>1 and Ve<1, the deviation amountof the azimuth error increases as the relative velocity becomes fartherfrom zero, and error in a calculation value of the mounting angledeviation θd increases.

Meanwhile, in a CW radar, in theory, an object of which the relativevelocity Vo is zero cannot be measured, and measurement accuracy whenthe relative velocity Vo is near zero is also low. Therefore, at therelative velocity Vo at which the deviation amount of thevelocity-azimuth curve C is almost zero, accurate measurement of theobject is difficult. Correction of the deviation in the azimuth anglebased on the deviation in the velocity-azimuth curve C is desired.

Therefore, in the weighting unit 33, in both of when Ve>1 and Ve<1,based on knowledge that the deviation amount of the azimuth error(θik−θok) increases as the azimuth θ becomes farther from 90+θr [deg],weight is supplied based on the estimated azimuth θok that is estimatedby the azimuth estimating unit 23.

For example, the weighting unit 33 may set the weight to be smaller asthe deviation amount of the azimuth error as a result of the vehiclevelocity error Ve of the own vehicle 40 increases. Specifically, asshown in FIG. 3, the deviation amount of the azimuth error as a resultof the vehicle velocity error Ve increases as the relative velocitybecomes farther from zero. Therefore, weight wk may be set to be smalleras the estimated azimuth θok becomes closer to that at which therelative velocity Vok of the object becomes farther from zero.

In addition, the weighting unit 33 may set the weight to be greater asthe estimated azimuth θok of the object becomes closer to a normaldirection that is orthogonal to a traveling direction of the own vehicle40. As shown in FIG. 3, an azimuth (an azimuth that is ±90+θr [deg])that is the normal direction that is orthogonal to the travelingdirection of the own vehicle 40 is an azimuth at which the deviationamount of the velocity-azimuth curve C that is attributed to the vehiclevelocity error Ve is smallest. Because the deviation amount of thevelocity-azimuth curve C decreases as the value of θok becomes closer toan azimuth that is the normal direction that is orthogonal to thetraveling direction of the own vehicle 40, the weight wk that issupplied is preferably increased.

Specifically, for example, when 0≤θok<θr, the weighting unit 33 maydecrease the weight wk as θok increases; when θr<θok<90+θr, theweighting unit 33 may increase the weight wk as θok increases; and when90+θr≤θok≤180, the weighting unit 33 may decrease the weight wk as θokincreases (unit is [deg] in each case). Here, the weight wk may bechanged in steps or may be continuously changed relative to theestimated azimuth θok. The weight wk may be determined in advance basedon simulations, experiments, and the like in which the vehicle velocityerror Ve is changed, and stored in the RAM of the signal processing unit20 as a map or a mathematical expression that corresponds to theestimated azimuth θok.

The correction value calculating unit 34 calculates the mounting angledeviation θd by calculating a weighted average value of the azimutherror (θik−θok) to which the weight wk is supplied by the weighting unit33. Then, based on the mounting angle deviation θd, an azimuthcorrection value θa that is a correction value of the azimuth θo that isthe azimuth of the object estimated by the azimuth estimating unit 23 iscalculated.

Next, an object detection process that is a main process performed bythe CPU of the signal processing unit 20 will be described withreference to a flowchart in FIG. 4. The signal processing unit 20periodically performs the object detection process shown in FIG. 4 atevery measurement cycle in which the radar wave is transmitted andreceived.

First, at step S101, whether an object is detected is determined.Specifically, sampling data of beat signals that amount to a singlemeasurement cycle that is acquired by the transmitting/receiving unit 12transmitting and receiving the radar wave is acquired, and whether anobject that reflects the radar wave is present is determined. Here, inthe single measurement cycle, sampling data that is related to alltransmission frequencies of the multifrequency CW is included. Whendetermined that an object is detected at step S101, the signalprocessing unit 20 proceeds to step S102. When determined that an objectis not detected, the signal processing unit 20 ends the process.

At step S102, the relative velocity Vok of the detected object to theown vehicle 40 is calculated for each observation point. Specifically, afrequency spectrum is calculated for each transmission frequency of themultifrequency CW and for each antenna that configures the antenna unit11 by frequency analysis being performed on the acquired sampling data.A frequency bin of the frequency spectrum acquired as a result indicatesthe relative velocity relative to the object that reflects the radarwave. Here, fast Fourier transform (FFT) may be used as the frequencyanalysis. Furthermore, regarding the N number of observation points atotal average value Vo of the relative velocity Vok is calculated. Afterstep S102, the signal processing unit 20 proceeds to step S103.

At step S103, the azimuth θok of the detected object relative to the ownvehicle 40 is estimated for each observation point. Specifically, basedon the frequency spectrum determined at step S102, an average frequencyspectrum is calculated for each antenna. Then, from the averagefrequency spectrum, a frequency bin in which a peak value at whichreception strength is equal to or greater than a threshold that is setin advance is detected is extracted. An azimuth estimation process isperformed for each frequency bin. Here, for the azimuth estimationprocess, a high-resolution estimation process such as multiple signalclassification (MUSIC) is preferably used. However, beam forming or thelike may also be used. Furthermore, regarding the N number ofobservation points, a total average value θo of the estimated azimuthθok is calculated. After step S103, the signal processing unit 20proceeds to step S104.

At step S104, the azimuth θo that is estimated at step S103 is correctedand the azimuth correction value θa is calculated. Specifically, theazimuth correction value θa is calculated by an azimuth correction valuecalculation process shown in FIG. 5 being performed.

In the azimuth correction value calculation process shown in FIG. 5,first, at step S201, the vehicle velocity Vc of the own vehicle 40 isacquired over the onboard LAN, and whether Vc exceeds a predeterminedvehicle velocity threshold V1 is determined. The vehicle velocitythreshold V1 is set to a value at which the velocity-azimuth curve C(see FIG. 3) that indicates the relationship between the relativevelocity Vo of the object and an observation azimuth θo has asufficiently large slope. When Vc>V1, the signal processing unit 20proceeds to step S202. When Vc≤V1 is determined, the signal processingunit 20 ends the process and proceeds to step S105 shown in FIG. 4.

At step S202, the observation point distribution P that is adistribution of two-dimensional data that is composed of the relativevelocity Vok and the estimated azimuth θok calculated at step S102 andS103 is generated. Subsequently, the signal processing unit 20 proceedsto step S203.

At step S203, the velocity-azimuth curve C is calculated based onexpression (2) above that is also shown in FIG. 2. The velocity-azimuthcurve C is a curve that is calculated based on the theoretical mountingangle θb of the object detection apparatus 10 and indicates therelationship between the relative velocity of the object and the azimuthof the object. Subsequently, the signal processing unit 20 proceeds tostep S204.

At step S204, the weight wk is supplied based on the estimated azimuthθok. The weight wk is supplied such that the weight increases as thedeviation amount of the azimuth error as a result of the vehiclevelocity error Ve of the own vehicle 40 decreases. Then, based onexpression (3) below that is also shown in FIG. 6, θdw that is aweighted average value is calculated.

$\begin{matrix}{{\theta\;{dw}} = \frac{\sum_{k = 0}^{N}\left( {\left( {{\theta\;{ik}} - {\theta\;{ok}}} \right)*{Wk}} \right)}{\sum_{k = 0}^{N}{Wk}}} & (3)\end{matrix}$

A broken line in FIG. 6 indicates the velocity-azimuth curve when avehicle velocity error is not present. A solid line indicates thevelocity-azimuth curve when a vehicle velocity error is present. In FIG.6, the vehicle velocity error is expressed by a difference in a velocityaxis (V axis) direction between the two velocity-azimuth curves. Inaddition, the azimuth error is expressed by a difference in an azimuthaxis (θ axis) direction between the two velocity-azimuth curves.

The deviation amount of the azimuth error that is attributed to thevehicle velocity error changes based on θ. For example, a deviationamount θe1 of the azimuth error may be greater than a deviation amountθe2 of the azimuth error (θe1>θe2). In this case, a value of the weightthat is supplied is increased as the deviation amount of the azimutherror decreases. The value of the weight that is supplied is decreasedas the deviation amount of the azimuth error increases.

As a result of weight being supplied in this manner, a degree ofcontribution of the observation point at which the deviation amount ofthe azimuth error is large can be decreased, and the degree ofcontribution of the observation point at which the deviation amount ofthe azimuth error is small can be increased. In the RAM of the signalprocessing unit 20, the weight wk that is set based on the deviationamount of the azimuth error as described above is stored in as a map incorrespondence to the estimated azimuth θok. The weight wk is read fromthe map based on the estimated azimuth θok that is estimated at stepS103. Subsequently, the signal processing unit 20 proceeds to step S205.

At step S205, the azimuth correction amount θa is calculated based onthe weighted average value θdw that is calculated at step S204. θdw isthe mounting angle deviation θdw of the object detection apparatus 10that is calculated with the weight wk being supplied to the azimutherror (θik−θok) for each observation point. Specifically, the azimuthcorrection value θa can be calculated by θa=a cos (Vo/−Vc)+θdw.Subsequently, the signal processing unit 20 ends the process andproceeds to step S105 shown in FIG. 4.

At step S105, object information that includes at least the relativevelocity Vo that is calculated at step S102 and the azimuth correctionvalue θa that is calculated at step S205 is generated and outputted toeach onboard apparatus over the onboard LAN. Subsequently, the processshown in FIG. 4 is ended.

As described above, according to the present embodiment, the weightedaverage value θdw is calculated by the weight wk being supplied based onthe estimated azimuth θok. The weight wk is decreased as the deviationamount of the azimuth error (θik−θok) attributed to the vehicle velocityerror Ve increases. In addition, the estimated azimuth is corrected bythe azimuth correction value using the weighted average value θdw as themounting angle deviation. Therefore, even when the vehicle velocityerror Ve is present, the deviation in the mounting angle can bemitigated and the azimuth of the object can be accurately calculated.Because the deviation in the mounting angle that occurs as a result ofthe vehicle velocity error Ve can be mitigated without the vehiclevelocity error Ve being actually measured, a new apparatus is notrequired to be added to the own vehicle 40 and the object detectionapparatus 10. Therefore, the present disclosure can be applied to anexisting object detection apparatus with relative ease.

According to the above-described embodiments, the following effects canbe obtained.

The object detection apparatus 10 is mounted to the own vehicle 40 anddetects an object by a reflected wave of a probe wave. The objectdetection apparatus 10 includes the velocity calculating unit 22 thatcalculates the relative velocity Vo of the object to the own vehicle 40,the azimuth estimating unit 23 that estimates the azimuth θ of theobject relative to the own vehicle 40, and the azimuth correcting unit30 that corrects the azimuth θo that is estimated by the azimuthestimating unit 23. The azimuth correcting unit 30 includes thevelocity-azimuth curve generating unit 32, the weighting unit 33, andthe correction value calculating unit 34.

For example, the velocity-azimuth curve generating unit 32 may generatethe velocity-azimuth curve C that indicates the relationship between therelative velocity Vo of the object and the azimuth θi of the object thatis calculated based on the theoretical mounting angle θb of the objectdetection apparatus 10 by expression (2) above that is also shown inFIG. 2. The weighting unit 33 supplies the weight wk to the azimutherror (θik−θok) that is the difference between the velocity-azimuthcurve C and the estimated azimuth θok for each observation point, basedon the estimated azimuth θok that is estimated by the azimuth estimatingunit 23. The correction value calculating unit 34 calculates theweighted average value θdw of the azimuth error to which the weight wkis supplied by the weighting unit 33, based on expression (3) above thatis also shown in FIG. 6. Then, the correction value of the estimatedazimuth θik is calculated using the weighted average value θdw as themounting angle deviation of the object detection apparatus 10.

As a result of the object detection apparatus 10, based on knowledgethat the deviation amount that occurs in the velocity-azimuth curve C asa result of the vehicle velocity error Ve changes based on the estimatedazimuth θok of the object relative to the own vehicle 40, the weightedaverage value θdw that is calculated by the azimuth error (θik−θok)being multiplied by the weight wk is calculated as the mounting angle ofthe object detection apparatus 10. Therefore, a calculation deviation inthe mounting angle of the object detection apparatus 10 that isattributed to the vehicle velocity error Ve can be mitigated. Inaddition, because the azimuth correction value θa of the object iscalculated using the mounting angle deviation θd, even when the vehiclevelocity error Ve is present, the azimuth of the object can beaccurately detected.

The weighting unit 33 may set the weight wk to be greater as thedeviation amount of the azimuth error (θik−θok) as a result of thevehicle velocity error Ve that is an error in the vehicle velocity Vc ofthe own vehicle 40 decreases. Because the mounting angle deviation θdwcan be calculated with a higher degree of contribution from theobservation point at which the deviation amount of the azimuth errorthat occurs as a result of the vehicle velocity error Ve is small, thedeviation in the mounting angle that occurs as a result of the vehiclevelocity error Ve can be reduced.

The weighting unit 33 may set the weight wk to be greater as theestimated azimuth θok that is estimated by the azimuth estimating unit23 becomes closer to the normal direction that is orthogonal to thetraveling direction of the own vehicle 40. Because the mounting angledeviation θdw can be calculated with a higher degree of contribution ofthe observation point that corresponds to the estimated azimuth θok atwhich the deviation amount of the velocity-azimuth curve C that occursas a result of the vehicle velocity error Ve is small, the deviation inthe mounting angle that occurs as a result of the vehicle velocity errorVe can be reduced.

Here, according to the above-described embodiment, an case in which theantenna unit 11, the transmitting/receiving unit 12, and the signalprocessing unit 20 are integrated in the object detection apparatus 10that is mounted to the bumper of the vehicle is described as an example.However, the present disclosure is not limited thereto. For example, thesignal processing unit 20 may be configured inside an electronic controlunit (ECU) of the own vehicle 40, and only the antenna unit 11 and thetransmitting/receiving unit 12 may be mounted to the bumper of thevehicle. In addition, when an imaging apparatus, a global navigationsatellite system (GNSS) reception apparatus, or the like is mounted tothe own vehicle 40, the signal processing unit 20 may be configured tobe capable of using data that is acquired from these apparatuses forobject detection, vehicle velocity detection, and the like.

The control unit and the method thereof described in the presentdisclosure may be implemented by a dedicated computer that is providedso as to be configured by a processor and a memory, the processor beingprogrammed to provide one or a plurality of functions that areimplemented by a computer program. Alternatively, the control unit andthe method thereof described in the present disclosure may be actualizedby a dedicated computer that is provided by a processor being configuredby a single dedicated hardware logic circuit or more. Stillalternatively, the control unit and the method thereof described in thepresent disclosure may be implemented by a single dedicated computer ormore, the dedicated computer being configured by a combination of aprocessor that is programmed to provide one or a plurality of functions,a memory, and a processor that is configured by a single hardware logiccircuit or more. In addition, the computer program may be stored in anon-transitory computer-readable storage medium that can be read by acomputer as instructions performed by the computer.

While the present disclosure has been described with reference toembodiments thereof, it is to be understood that the disclosure is notlimited to the embodiments and constructions. The present disclosure isintended to cover various modification examples and modifications withinthe range of equivalency. In addition, various combinations andconfigurations, and further, other combinations and configurationsincluding more, less, or only a single element thereof are also withinthe spirit and scope of the present disclosure.

What is claimed is:
 1. An object detection apparatus that is mounted toa vehicle and detects an object by a reflected wave of a probe wave, theobject detection apparatus comprising: a velocity calculating unit thatcalculates a relative velocity of the object to the vehicle; an azimuthestimating unit that estimates an azimuth of the object relative to thevehicle; and an azimuth correcting unit that corrects the azimuth of theobject relative to the vehicle that is estimated by the azimuthestimating unit, wherein the azimuth correcting unit includes avelocity-azimuth curve generating unit that generates a velocity-azimuthcurve that indicates a relationship between the relative velocity of theobject and the azimuth of the object that is calculated based on atheoretical mounting angle of the object detection apparatus, aweighting unit that supplies weight to an azimuth error that is an errorbetween the velocity-azimuth curve and the estimated azimuth, based onthe azimuth that is estimated by the azimuth estimating unit, and acorrection value calculating unit that calculates a correction value ofthe estimated azimuth by calculating, as an actual mounting angledeviation of the object detection apparatus, a weighted average value ofthe azimuth error to which the weight is supplied by the weighting unit.2. The object detection apparatus according to claim 1, wherein: theweighting unit increases the weight as a deviation amount of the azimutherror as a result of a vehicle velocity error that is an error in avehicle velocity of the vehicle decreases.
 3. The object detectionapparatus according to claim 1, wherein: the weighting unit increasesthe weight as the estimated azimuth becomes closer to a normal directionthat is orthogonal to a traveling direction of the vehicle.
 4. Theobject detection apparatus according to claim 2, wherein: the weightingunit increases the weight as the estimated azimuth becomes closer to anormal direction that is orthogonal to a traveling direction of thevehicle.
 5. An object detection apparatus that is mounted to a vehicleand detects an object by a reflected wave of a probe wave, the objectdetection apparatus comprising: a processor, wherein the processor isconfigured to: calculate a relative velocity of the object to thevehicle; estimate an azimuth of the object relative to the vehicle; andcorrect the estimated azimuth of the object relative to the vehicle,wherein the processor is further configured to: generate avelocity-azimuth curve that indicates a relationship between therelative velocity of the object and the azimuth of the object that iscalculated based on a theoretical mounting angle of the object detectionapparatus; add weight to an azimuth error that is an error between thevelocity-azimuth curve and the estimated azimuth, based on the estimatedazimuth; and calculate a correction value of the estimated azimuth bycalculating, as an actual mounting angle deviation of the objectdetection apparatus, a weighted average value of the azimuth error towhich the weight is supplied.
 6. The object detection apparatusaccording to claim 5, wherein: the processor is further configured toincrease the weight as a deviation amount of the azimuth error as aresult of a vehicle velocity error that is an error in a vehiclevelocity of the vehicle decreases.
 7. The object detection apparatusaccording to claim 5, wherein: the processor is further configured toincrease the weight as the estimated azimuth becomes closer to a normaldirection that is orthogonal to a traveling direction of the vehicle. 8.The object detection apparatus according to claim 6, wherein: theprocessor is further configured to increase the weight as the estimatedazimuth becomes closer to a normal direction that is orthogonal to atraveling direction of the vehicle.